In conventional magnetic bearings, the central shaft of the rotor has a stack of magnetic laminations around its periphery in which the laminations are in the form of washers which are coaxial with the central shaft and which enable the magnetic field created by the electromagnets of the magnetic bearing's stator to loop through a material of better magnetic quality than the central shaft.
When a magnetic bearing is of large diameter, the tangential speed of the laminations at the periphery of the rotor nevertheless sets up non-negligible stresses if the laminations are washer-shaped, and given that the mechanical properties of the laminations are relatively poor, the speed of rotation of the rotor must be limited.
Further, large sized sheet material is required for making washer-shaped laminations of large diameter, and when said laminations are cut out from such sheets, there is a high degree of wastage.
Also, in practice, it is particularly difficult to make large sized sheets which are simultaneously very thin and also of high magnetic quality.
Preferred embodiments of the invention seek to remedy the above drawbacks and to provide a large diameter radial magnetic bearing which is cheap to manufacture, which suffers from small eddy current losses, and in which the speed of rotation of the rotor may be high.